The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In modern motor vehicle transmissions employing a plurality of planetary gear sets, radially stacked or nested planetary gear sets enable a more axially compact transmission configuration. While highly desirable from a packaging standpoint, this arrangement places the outer planetary gear set and especially the outer planet gear carrier a relatively significant distance from the source of lubrication which is generally the central transmission shaft. This distance, alone, can reduce the volume of transmission fluid (lubricant) flow to the outer planetary gear set. Moreover, in certain cases and during certain modes of operation, the outer carrier may be stationary and the flow of transmission fluid (lubricant) against gravity to the topmost pinion needle bearing and, to a lesser extent, the side pinion needle bearings, may be further reduced.
Such flow is, however, critical to bearing durability and longevity from not only a lubrication standpoint but also from a heat dissipation standpoint as planetary gear pinions in modern motor vehicle automatic transmissions may reach speeds of 12,000 r.p.m. and above during certain operational conditions.
Thus it is critical that suitable lubrication be provided to the pinion needle bearings of the outer planetary gear set of a stacked planetary gear assembly. The present invention is so directed.